I had to think about this. There's "where I hang out most" and "what I appreciate most as a resource" and "where I point other people to most often" *koff* whichonedoIbuy *koff*...
My favorite section is probably
News. I'm delighted that I can google search for cutting-edge details about ereaders or copyright law or ebook stores... and find a thread I've already been following. Not sure how it could be improved. Maybe more labels? Law/ devices/ ebooks/ resources/ software?
I've only been a member for the last 4 years, but I remember running across Mobileread much earlier than that. I've been peripherally dealing with ebooks since about 1994 when I got one of the Gutenberg collections on CD, and Mobilearead was always high in the search results when I looked for more information. I used the wiki more than I noticed the forums. (I'd love some of us to spend more time tweaking the wiki. Everything's changed so fast in the last few years.)
Happy anniversary, MR! Here's hoping for ten more years coming up!